1. Field of the Invention
The present invention relates to a trim and tilt mechanism for angularly moving an outboard engine into a desired trimmed position and also into a tilted position above the surface of the water.
2. Description of the Relevant Art
Generally, an outboard engine is detachably mounted on the stern of a boat by a pair of transom brackets and a pair of swivel brackets pivotally coupled to the transom brackets. Outboard engines are often associated with trim and tilt mechanisms as disclosed in U.S. Pat. No. 3,581,702, for example. The disclosed trim and tilt mechanism angularly moves the outboard engine vertically so that the angle of the outboard engine in the water is adjusted with respect to the boat. In addition, the trim and tilt mechanism also serves to absorb shocks or impacts when the outboard engine happens to be hit by an object in the water. The trim and tilt mechanism has a hydraulic cylinder comprising a cylindrical casing and a piston rod reciprocally movable in the cylindrical casing. The piston rod has an upper free end pivotally coupled to the swivel brackets, and the casing has a lower end pivotally coupled to the transom brackets. When the hydraulic cylinder operates, the piston rod is reciprocally moved thereby to turn the outboard engine vertically about a horizontal axis.
The hydraulic cylinder is supplied with working oil which is stored in a tank. If the tank has a large storage capacity, then it reduces the installation space available for the hydraulic cylinder. One solution is to employ two relatively small oil tanks, and to attach one of the tanks, referred to as an auxiliary tank, to the cylindrical casing. This arrangement allows the trim and tilt mechanism to be designed with greater layout flexibility for use with outboard engines. It is advantageous if the auxiliary tank and the cylindrical casing are cast as a unitary structure. According to one casting process, a sand core is set in the cavity of a mold assembly, and after an auxiliary tank and a cylindrical casing are cast, the sand core is broken and the pieces of the broken sand core are removed. Unnecessary portions may be cut off the auxiliary tank and the cylindrical casing. The sand core pieces and the cut-off fragments or chips are taken out through a cap opening in the upper end of the auxiliary tank. If the cap opening is large enough, the sand core pieces and the cut-off fragments cap easily be removed therethrough. However, the wall which interconnects the casing and the auxiliary tank becomes so thin that its mechanical strength is not large enough.